There are information processing apparatuses known for accepting a write request including a data and storing the data included in the accepted write request into a storage device.
As one of the information processing apparatuses of this kind, the information processing apparatus described in Patent Document 1 acquires a hash value by inputting the data to a hash function at the time of storing a data into a storage device. Then, when the storage device has not stored a hash value identical to the acquired hash value, the information processing apparatus correlates the data, the hash value, and information of referenced times denoting the number of times the data has been referenced; then, it stores the correlated items into the storage device.
On the other hand, when the storage device has stored a hash value identical to the acquired hash value, the information processing apparatus changes the information of referenced times correlated with the hash value and stored in the storage device such as to add one to the number of times denoted by the information of referenced times. According to this information processing apparatus, because it is possible to avoid repeatedly storing the identical data into the storage device, it is possible to reduce the data amount stored in the storage device.    [Patent Document 1] JP 2007-234026 A
However, there are times when the hash function outputs an identical hash value even though different data are inputted (collision occurs in the hash value). Therefore, in the above information processing apparatus, when collision has occurred in a hash value, there is a problem that two different data are mistakenly recognized as an identical data to give rise to occurrence of the case that one of the data disappears.
Further, supposing that the above information processing apparatus is configured to detect whether or not data are identical by directly comparing at least parts of two data of an identical hash value, there is another problem that the processing load becomes too heavy on the information processing apparatus.